1. Field of the Invention
The present invention relates to a solenoid valve fixing structure, more particularly, a solenoid valve fixing structure constructed as a module comprised of a solenoid valve, a check valve and an air filter. They are components of an apparatus for suppressing evaporated fuel gas emission, which protects the emission of evaporated fuel gas into the atmosphere. The evaporated fuel gas is a gas evaporated from a fuel tank of a vehicle, for example.
2. Description of the Prior Art
A system for reserving hydro-carbon gas using an activated carbon canister is well known, in which a hydro-carbon gas evaporated from the fuel in a fuel tank, due to engine heat or external heat, is temporally reserved in an activated carbon containing canister, and while the vehicle is running, the reserved gas is sent into the intake manifold of the engine of a vehicle so as to be burned out, for protecting the emission of the hydro-carbon gas into the atmosphere.
A representative apparatus for suppressing evaporated fuel gas emission in the prior art, in which hydro-carbon gas is reserved in an activated carbon canister is explained below, referring to FIG. 4, which is a schemtaic diagram of an apparatus for suppressing the evaporated fuel gas emission of the prior art.
Reference numeral 21 denotes a fuel tank, the fuel tank is connected with a separator 23 through a channel 22. The evaporated gas from the fuel tank is separated into a liquid component and a gas component in the separator 23. Reference numeral 24 denotes a pressure sensor for diagnosis, which detects pressure change for detecting leakage of the evaporated fuel gas while the vehicle is running. Reference numeral 25 denotes a canister containing activated carbon for reserving the evaporated fuel gas temporally. The canister 25 has an air introducing hole 26, an evaporated fuel gas introducing hole 27 and an outlet hole 28 of the reserved fuel gas, which is lead to an intake manifold 29 of the engine. The purge quantity of the evaporated fuel gas from the canister 25 to the intake manifold 29 is controlled by a purge valve 30.
A solenoid valve 31 controls the opening and closing of an air introducing hole 26 of the canister 26. Ordinarily, the solenoid valve 31 keeps an opening state so that the air introducing hole 26 is open to the atmosphere. This solenoid valve 31 is closed, only when the communication from the atmosphere shall be cut off at a diagnosis of the apparatus. The solenoid valve 31 is connected to the air introducing hole 26 through an air hose 32.
The solenoid valve 31 is connected with an air filter 33 and a check valve 35 through piping 34. The air filter 33 serves to clarify the air to be introduced into the solenoid valve. The check valve 35 opens when the pressure in the fuel tank increases, for example, during an oil feeding into the fuel tank. As a result, the increase of pressure in the fuel tank is suppressed, and the oil can be fed easily into the fuel tank 21.
The solenoid valve 31, the check valve 35 and the air filter 33 are independently fixed, for example, to a side frame of a vehicle, by means of bolts, for example. They are interconnected through piping 34.
The function of the apparatus for suppressing evaporated fuel gas emission of this prior art is explained below.
The gas component of the fuel evaporated from the fuel tank 21 is separated by the separator 23 as an evaporator fuel gas, and is reserved in the canister 25 temporally.
The air introducing hole 26 of the canister 25 is maintained to be open to the atmosphere by the solenoid valve 31, but is closed at a diagnosis of the apparatus. While it is closed, a measurement of the pressure is carried out by the pressure sensor 24, and a diagnosis whether a leakage of evaporated fuel gas according to a break down of piping, for example, is taking place or not is made.
While the vehicle is running, the evaporated gas reserved in the canister 25 is sucked by the negative pressure of the intake manifold 29 through an outlet hole 28 of the canister. The sucked fuel gas is sent to the engine of the vehicle to be burned out therein. Thus the emission of the hydro-carbon gas into the atmosphere is protected. The "negative pressure" is defined as "pressure lower than atmospheric pressure" in this specification and claims.
The apparatus for suppressing evaporated fuel gas emission in the prior art has drawbacks that the solenoid valve 31, the check valve 35 and the air filter 33 must be independently fixed, for example, to a side frame of a vehicle. Hence, many supplemental connecting elements, for example, bolts or piping are required, for their installation. This means that the number of fabrication elements as well as the number of steps for installing them are large, as a result, the fabrication performance is low.
Additionally, the piping 34 is the longer, the possibility of leakage of evaporated fuel gas is the higher, thus, the total reliability of the system becomes lower accordingly.
The piping 34 for communication with the atmosphere must have a larger diameter. Thus the solenoid valve 31, which opens and closes the piping 34, tends to generate noisy sound, when it operates. The reduction of the noisy sound was difficult.
An improvement of the connection between a solenoid valve and a canister of the prior art is disclosed in Japanese patent applications JP-A-6-73254 and JP-A-3-37368. And a module, in which a solenoid valve and air filter, etc, are fixed to a fixing bracket of a canister, which serves to fix the canister to the vehicle is disclosed in Japanese patent application JP-A-9-25855. However, they do not disclose a module comprised of a solenoid valve, a check valve and a canister, for the purpose of reducing the number of fabrication elements as well as to improve the fabrication performance, and to decrease the size of the apparatus.